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| # Bazel `rules_shell` | ||
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| [`rules_shell`](https://github.com/bazelbuild/rules_shell) is an experimental Bazel ruleset maintained by the Bazel team that enables modern, hermetic support for writing Bazel targets using shell scripts. | ||
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| ## Purpose | ||
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| The goal of `rules_shell` is to make working with shell scripts in Bazel more robust and reproducible, similar to how Bazel handles other languages like Go (`rules_go`) or Python (`rules_python`). | ||
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| ## Key Features | ||
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| - **Hermetic `sh_binary` and `sh_test` rules** | ||
| - Declare and manage script dependencies explicitly | ||
| - Scripts only access files and tools declared as inputs | ||
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| - **Shell toolchain support** | ||
| - Customizable shell interpreter (e.g., specific `bash` version) | ||
| - Cross-platform support via toolchain configuration | ||
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| - **Reproducibility and sandboxing** | ||
| - Ensures scripts only access declared inputs | ||
| - Improves remote caching and build determinism | ||
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| ## Example | ||
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| Here’s a simple example of a shell binary using `rules_shell`: | ||
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| ```python | ||
| load("@rules_shell//shell:defs.bzl", "sh_binary") | ||
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| sh_binary( | ||
| name = "hello", | ||
| srcs = ["hello.sh"], | ||
| data = [":greeting.txt"], | ||
| deps = ["@bash//:bin/bash"], | ||
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Collaborator
There was a problem hiding this comment. I don't think this could be realized as the script needs some shebang that would run first. If we want it to be truly hermetic, we would need to involve a launcher binary, a simple dep wouldn't help. |
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| ) | ||
| ``` | ||
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| ## Dependancies | ||
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| Please note that rules_shell depends on bash outside of the Bazel sandbox | ||
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| ``` | ||
| _DEFAULT_SHELL_PATHS = { | ||
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Collaborator
There was a problem hiding this comment. We should mention that these are the default paths, but that you can register your own toolchains and/or set |
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| "windows": "c:/msys64/usr/bin/bash.exe", | ||
| "linux": "/bin/bash", | ||
| "osx": "/bin/bash", | ||
| "freebsd": "/usr/local/bin/bash", | ||
| "openbsd": "/usr/local/bin/bash", | ||
| } | ||
| ``` | ||
| [sh_config.bzl](https://github.com/bazelbuild/rules_shell/blob/main/shell/private/repositories/sh_config.bzl#L18) | ||
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Thanks for taking a stab at this, but I fear that we don't really live up to this promise just yet. This ruleset is more or less a faithful port of the formerly native shell rules, it's not (yet) more robust or reproducible.
There is an active proposal for integrating
ctx.actions.run_shellwith rules_shell as well as providing a PATH of hermetic shell tools. I would like to wait for that to be implemented before we claim this.There was a problem hiding this comment.
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Is there any README.md that you'd be able to add to give some indication to how rules_shell is supposed to be used?
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@filmil
Thanks for your response
Sorry I'm not sure who you are asking
In general, this merge request was mostly intended to highlight that rules_shell isn't well documented. In particular, it is unclear [at least to a fool like me] what rules_shell is intending to achieve.
I strongly suspect that that team who wrote rules_shell did have a clear intent and do understand what rules_shell all about. - It would really help others to document this even minimally. It might even help the experts who do understand to stay on track :)
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The question was for @fmeum . It would be nice if a maintainer would bootstrap a README.md with main points to know about the rule set.